For a conventional type high-frequency heating apparatus, there are a type having only one function of high-frequency heating and a combination oven provided with a convection heater that generates a hot air in addition to high-frequency heating, and a high-frequency heating apparatus that a high frequency and steam can be supplied to a heating chamber is also discussed. For a high-frequency heating apparatus to which a steam generating function is added, various methods including a method of providing a boiler outside a heating chamber and leading steam generated from the boiler into the heating chamber are proposed.
Recently, a high-frequency heating apparatus the volume of the heating chamber of which is increased by arranging an operator panel at a hatch, arranging a control circuit at the bottom, using the whole front of the body for a hatch and further thinning a wall forming a heating chamber up to the minimum has been adopted.
For a water supply method for generating steam of the high-frequency heating apparatus provided with a steam generating function, there are a method of directly supplying water to a water reservoir heated by a heater and a method of supplying water from a water tank connected to a steam generator. However, in the method of directly supplying to the water reservoir, when water in the reservoir is heated, it is evaporated and condensed, a so-called scale such as calcium and magnesium included in the water is deposited and adheres to the inside face of a heater and the reservoir. Therefore, the thermal efficiency of evaporation is deteriorated, the reservoir is required to be frequently cleaned and it is not desirable sanitarily. Every time an object to be heated is heated, water is required to be supplied to the reservoir, a heating process itself is troublesome and it is a difficulty of such an apparatus.
In that respect, a method of supplying from a water tank is excellent in ease of use, however, the method of using a water tank also has the following problems. First, in case a water tank cannot be detached from a high-frequency heating apparatus, the inside of the water tank is insanitary. When a water tank is simply attached to a high-frequency heating apparatus, the body size of the high-frequency heating apparatus is expanded, the area for installing the apparatus is expanded and the saving of space becomes impossible. Further, when a water tank is arranged inside a high-frequency heating apparatus, water may penetrate into a control circuit into which water should not penetrate and when penetrating water remains in the body, a sanitary problem is caused. Further, as a heating chamber and a water tank are arranged close, heat caused as a result of heating an object to be heated from the heating chamber may be transmitted into the water tank.
As described above, it is desirable from the viewpoint of space for installation that a water tank is arranged in a high-frequency heating apparatus compactly, however, from the viewpoint of the leakage of water from the water tank and the transmission of heat from a heating chamber, it is desirable that the water tank is provided outside the high-frequency heating apparatus. Therefore, the arrangement of a water tank with ease of use by which all problems can be solved at a time has been desired. Particularly, the limit of the usable temperature of a pump for supplying water in a water tank to a steam generator is low and overheat by the transmission of heat is required to be prevented possibly.